A variety of chemical and mechanical methods for controlling fertility and for preventing pregnancy are known. Approaches such as sterilization, the use of condoms, intrauterine devices (herein "IUD"), intracervical devices, (herein "ICD"), spermicidal creams and jellies, foam tablets, and oral pills are currently available to prevent pregnancy. These methods, though effective to a variable extent, also have limitations. Most of these devices require constant motivation on the part of the user and some approaches such as sterilization, ICDs and IUDs require specialized medical attention.
Oral contraceptives are a popular method of contraception, but have many undesirable side effects and require the daily ingestion of a tablet. The use of a medicated intracervical or intrauterine device as a means of administering effective contraceptive steroids through a vaginal or uterine route is seen as a means of overcoming some of these drawbacks.
It is known that intrauterine devices can provide a system for timed release, local administration of a drug. For example, IUDs having a drug-releasing erodible outer layer or partial covering have been suggested as a means for delivering drugs to the uterus. In one example of the foregoing, it has been suggested that a small section of a Lippes loop be coated with an erodible polymer containing an appropriate drug. In another example, a sleeve of bioerodible material, having a contraction inducing drug distributed therein, is attached to an IUD that is especially constructed to deteriorate and be ultimately expelled from the uterus after use.
U.S. Pat. No. 4,341,728 to Robertson, et al. describes a particularly useful medicated IUD. According to that invention, an intrauterine controlled release drug delivery article is associated with a proven IUD platform. The drug release article is constructed for attachment to a known platform, which is nonmedicated and relatively stable. The drug release article can be for example a molded sleeve tightly secured on a stem of an extant IUD.
In the Robertson et al. invention, an outer drug permeable tube surrounds the drug release sleeve, thus controlling the rate of administration of the drug contained in the drug release sleeve. RTV silicone rubbers are employed as the base or carrier material of the sleeve in the IUD disclosed by Robertson et al. Removal of the fillers from commercially available silicone rubber, for example by centrifuging, makes the silicone rubber used by Robertson et al. more satisfactory for drug release. The use of the outer drug permeable tube which fits tightly over the drug release sleeve also imparts structural integrity to the fillerless silicone rubber of the sleeve which permits it to be easily handled without deterioration prior to insertion in the uterus.
Medicated IUDs as described in U.S. Pat. No. 4,341,728 are useful but have several drawbacks. An IUD is designed to be inserted into the woman's uterus which makes positioning of the IUD important and requires insertion and removal by a qualified health professional. Known IUDs are also often associated with undesirable bleeding of the endometrium lining due to irritation.
Medicated intracervical devices (ICDs) which are introduced into the cervical canal just beyond the cervical os in order to prevent pregnancy are also known and have also been used to release contraceptive hormones i.e., El Mahgoub, S., Contraception, 1982, Vol. 25, No. 4, p. 357-374. Like medicated IUDs. Medicated ICDs can be useful for the inhibition of fertility but are also useful in treating and medicating other conditions of the female reproductive system.